Double acting jaw crusher



o. c. GRUENDER DOUBLE" ACTI G JAW CRUSHER Oct. 4, 1938.

Filed May 19, 1934 6 Sheets-Sheet l I bet-4,1938. o. c. GRUENDER 2,DOUBLE ACTING JAW CRUSHER Filed May 19, 19:54 6 sheets-sheet 2 f A J 5@L G E Oct. 4, 1938. o. c. GRUENDER DOUBLE ACTING JAW CRUSHFTRJitfiorngyfi Filed May 19, 1934 Oct. 4, 1938, ,o..c. GRUENDER 2,131,801

DOUBLE ACTING JAW CRUSHER Filed May 19, 1934 a Sheets- Sheet 5 50a?" 6.fr aerzakr' 193& o. c. GRUENDER 7 131,801

DOUBLE ACTING JAW CRUSHER Filed May 19, '1934 6 Sheets-Sheet 6 .[rzvemor@5007 6. 'raerzokr @MRCMR Passes on. 4,1933:

\ NITED STATES nonnns some nw cnnsnnn I Oscar C. Gruender, Milwaukee,Wisgassignor to Nordberg Manufacturing 00., Milwaukee, Win, acorporation of Wisconsin v Application May 19, 1934, Serial No. 126,49115 Claims. (or. 83-53) My invention relates to an improvement in jawcrushersr and particularly to a double .jaw crusher in which twonormally flxed=jav s are acted upon by a single moving jaw structure;the

moving jaw structure having a crushing'face opposed to eachof thenormally fixed jaws. One purpo'seis the provision of improved means forsimultaneously crushing particles of different size in a single crusher.Another object is we provision of means for delivering simultaneouslytwo different sizes of produce from a single crusher. Another object isthe provision-of improved jaw actuating means for a jaw crusher.

Another object is the provision of improved feeding means for a'iawcrusher. Another object is the provision of improved lubricating meansfor a jaw crusher. Another object is the provision of improved yieldingrelease means for permitting a jaw or crushing memberto release when itis opposed by a predetermined excess crushing stress.

Another object is the provision of improved means for adjusting theposition of the fixed jaw or jaws. Another object is to provide foradjustment of the feed apertures or crushing cavities. 1

Other objects will appear from time totime in the course of thespecification and claims.

I illustratemy invention more or less dia-' grammatically in theaccompanyi drawings, wherein- Figure 1 is a side elevation; Figure 2 isa. section on the line 2-2 of Figure 1;

Figure Figure 2; Figure Figure 3; Figure Figure 3;

3 is a; section onthe line 3-3 of 4 is a section on the line ll of 5 isa section on the line 5 5 of jaws; and

Figures 7, 8 and'9 are partial sections, similar to Figure 3, throughvariant forms of feeding or feed limiting means.

A link connection between the shafts H and H".

Like elements are indicated by like symbols throughout the specificationand drawings.

Referring to the drawings, A generally indi-' catesthe side wall of aframe structure which includes lower base or reinforcing flanges A andstrengthening webs A. The frame includes two sides having upwardly andinwardly inclined edge 7 Figure 6 is a motion diagram of one of the Fig.10 is a diagrammatic view illustrating the transverse apertures A",reinforced, by flanges A the purpose for which will later appear.

Projecting outwardly from each side of the frame is a spring enclosurewhich includes a wide member B lying in the general plane of theinclined edge A of the frame. It is connected to inclined portions Bwhich extend inwardly and terminateas at l? where they are lost in thegeneral level'of an outward projection or offset .8 of the side frame Awhich offset'is shown, for example, in Figure 5. The member B isapertured, exteriorly of the side of the frame, as at B 3*.' As will beclear from Figure 4 the member B extends on both .sides of the sideframe member and it is inwardly apertured as at B5 to permit the passageof bolts therethrough.

0 indicates cylindrical sleeves formed in the side frame members inwhich are positioned hearing sleeves C which may be flanged as at C andheld in position as by the bolts 0. C are bushings or sleeves which may,for example, be of bronze or any other suitableanti-frictional material.It will be observed that ,two of these sleeves C are employed for eachbearing, each onebeing flanged at its end as at (3 and extendinginopposite directions into the sleeve 0 but separated if desired, leavinga. channel C the purpose of which will later appear.

D generally indicates a drive shaft which includes portions D Dconforming to the inner faces of the sleeves C and provided with acentral eccentric portion D. D is anysuitable drive pulley which may be'keyedor otherwise secured upon and held against rotation in relation tothe shaft D as by the key D. D may, if desired, be of suflicientweightto serve as a fly wheel. Secured to each end of the shaft D exteriorlyof the bearings above described are maze members D which are surroundedbyand interpenetrate with opposed fixed maze members D The purpose ofsaidmaze is to prevent the escape of oil or lubricant and prevent thepenetration of dust, grit or the like.

E generally indicatesv a moving jaw or head structure. It includesupwardly and inwardly inclined jaw supporting members E E which areherein shown as joined by a transverse upper portion E as shown inFigure 3. They are inwardly strengthened and supported by-ribs E whichare in connection with an inner box-like enclosure E having side wallsE, a top wall E" and a removable bottom plate E Positioned within thisbox structure are wear taking side plates or liners E the upwardposition of which is limited by shoulders E". "They are locked inposition, when the closure plate E is in position, by the bolts E whichpenetrate the said plate. These members may be of bronze or any othersuitable anti-frictional and wear taking material. The

moving jaw E has the upwardly extendingend walls E E", to retain thecrushing material. The lower portion of the end walls .having the liningplates E E", held in place by the lugs E E, and also by the upper linerplates E E, which are held in place by the cap screws E E" indicates thedividing line between the two lining plates.

Slidable between the opposed liner plates E is a sleeve G which has aninner cylindrical surface G provided with any suitable bushings orsleeves G which surrounds and conforms to the exterior of the eccentricD of the shaft D. vThe exterior of the member G is provided with planesurfaces G which slide upon the liner plates E Secured to the ends ofthe walls E and E are closure members G G which may be bolted, for ex-.

ample, by the bolts G The member G includes flange portions G" spacedout to receive penetrating flanges G of rings G9 which surround theinner ends of the bearing sleeves C It will be seen that a slip fitbetween the members G and G is thus provided which prevents escape ofoil and excludes dust or grit.

The above described head structure is supported on the frame in thefollowing manner. A plurality of movable links or groups of links orstruts are employed, generally indicated as 1-1. These links are pivotedat their lower ends, as

shown in Figures 3 and 5, to the fixed shafts H which may be providedwith any suitable axial oil passages H and radial oil passages H. Hindicates a bearing sleeve rotatable about the fixed shaft H and havingthe wearing bushings H The links H, H, may be either integral with orsecured to the sleeve H The links H terminate in eyes H, herein shown asintegral, inwhich are positioned a shaft H", such shaft being heldagainst rotation in relation to the eyes H as by set screws or lookingmembers H penetrating notches or apertures H. H are wearing bushingswithin the sleeve H of the swinging crushing jaw member E, in which theshaft H" rocks. H is any suitable axial oil aperture for the shaft H andH is a radial oil aperture. Any suitable fitting H may be employedwhereby oil or any other suitable lubricant may be admitted. Apertures Aare provided in the side walls of the frame A to allow the use of agrease gunfor the fittings H It will be observed, as from Figure 3, thattwo pairs of links are employed, one underlying each crushing face ofthe member E, the links being inclined upwardly and inwardly toward eachother. They so support the swinging crushing member E that none of itsweight is supported by the eccentric.

Whereas any suitable oil fittings may be employed for lubricating thebearings for the links or struts H, I provide a separate and independentlubricating system for the bearings of the shaft D. I illustrate, forexample, the member D in Figure 2 as formed with gear teeth J which arein mesh with a driven pinion J which actuates any suitable pumpstructure, the details of which form no part of the present inventionbut which may be housed in the housing J As the gear J rotates with theshaft D this pump is constantly actuated during the operation of thecrusher, thereby forc ing oil through the pipe line J to one of thebearing sleeves C The oil then passes around the channel C into theradial aperture J in the shaft D; itthen passes through the axialaperture J and lubricates the eccentric t rough the aperture J 6 and theopposite bearin sleeve C through the aperture J The oil which collectsin the bottoin of the swing jaw enclosure E flows by gravity through aflexible pipe J 8 back to a supply oil tank not shown. J is a supplypipe from the tank to the pump.

The swing jaw or head structure E is provided with a plurality ofremovable replaceable crushing plates K, K each With a lower bevelledface K and an upper bevelled face K. The lower bevelled faces Kpenetrate overhanging notch members K formed at the lower edgesof thewalls E and E The two plates are then unitarily locked in position bythe transverse member K with its feed separating upward projection orplate K through which pass threaded rods or bolts K which have nuts K atthe lower ends recessed in the transverse top portion E of the head E.Nuts K at the upper ends serve to lock the assembly in place and thetransverse member K is thereby thrust downwardly against the upper edgesof K and K locking them firmly in position.

I provide two separate individual norm-ally fixed crushing jaws opposedto the moving head E. I illustrate these jaw structures generally as L,L each such jaw structure being rotatable about a normally fixed axis orshaft L Each jaw includes a sleeve L and a rearward projection Ltherefrom and a forward and considerably shorter projection L Theprojection L has a lower notch L to receive the lower edge of thecrusher plate L", the upper edge of which, bevelled as at L is engagedby a correspondingly bevelled locking member L which also engages thebevel L of the projection L bolts with heads L whereby the bevelledmember L is moved into locking position, thrusting and holding the plateL into the position in which it is shown in Figure 3. The location ofthe shaft L is shown asadjustable. Referring, for example, to Figures 1and 3, the shaft L may be secured to the bearing supports L slidablymounted in the recesses A A of the frame, A plurality of shims L may beemployed to space the member L out at any desired position ofadjustment, as shown in the recess A No shims are shown in the recess Aso that the upper hinged end of the fixed jaw L is set at the closestposition to the moving jaw while the upper hinged end of the fixed jaw Lis set at its farthest position from the moving jaw E. The bolts L withthe nuts L and L are effective to lock the parts firmly in the desiredadjustment. The bolts L are weakened by the groove L to provide a safetybreaking point in the event of anyuncrushable material lodging in theupper part of the throat between the crushing jaws. L is an' inclinedprotecting plate tending to deflect the materialfed into the crushingcavity and to protect the member L L L etc., from the battering offalling particles which may be fed to the crushing cavity.

I'also provide for an adjustment of the lower end of the normally fixedposition of the jaws L,

L as follows. The side walls of the main frame are bridged by atransverse member M which lies against the member B and is heldby'springs M 'The springs are held under compression between L are screwthe lugs N of the sleeve N. The four outwardly projecting lugs N areapertured to receive four screw bolts which screw into the lugs W of thesleeve N. By loosening these bolts the cap plate N can be turned ineither direction with a bar passed between the projecting lugs N theslots N of the flange N engaging the lugs N of the sleeve N, will rotatethe sleeve and provide any desired adjustment. After the adjustment hasbeen made the bolts N" are tightened and take up any slack in thethreads M The lower ends of the fixed jaws have a convex surface L whichis held in contact with the lower face N of the sleeve N by a hook endof the bolt-O engaging a rib L of the fixed jaw. The bolt extends upthrough the slot L in the jaw and an aperture in the bottom N of thesleeve. A springO compressed between the bottom N and the washer O andnut 0 serves to hold the convexsurface L in contact with the adjustingsleeve. This adjustment may be made to allow for wear or to allow for awide range of settings to meet various crushing requirements. The lefthand jaw L isshown set for fine crushing and the right hand jaw L is setfor coarse crushing. The heavy coal springs M of which there are twelvefor each stationary jaw, afford a yielding means for the escape of anyuncrushablematerial which may happen to enter the crusher.

A feed hopper P supported on the frame A by brackets P P is providedwith a center wall P flared at the lower portion as at P to divide thestream of material and direct it to each crushing cavity.

Referring to Figure 7, I illustrate in the place of the members K and Ka unitary member S which includes a transverse locking member S appliedto the upper edges of the jaw plates K and K Integral with it is theupper web or partition S which is expanded at its top to form a bracketor plate support S upon which may be mounted the feeding plate S? whichmay be of any suitable form but is herein shown as having raised rims 5S represents a feed receiving partition at a level above the plate 8. Itis provided with a central aperture S and forms part of a feeding hopperherein shown as having verticallsides S in which feed is received fromthe delivery chute not shown. It will be understood, of course, that theform of the hopper S may be varied. I find it advantageous, however, ato have a feed aperture, such as S", with a limited diameter, verticallyaligned with the plate S Material escapes over one edge of the plate 8*into one crushing cavity and over the other edge into the other, aswill-be clear ffom Figure '7.

. S is any suitable confining chute positionedbelow the partition S andoverlying the members L This prevents or limits the escape of dust orflying particles.

Referring to Figure 8, T generally indicates a feed.- box or hopperreceiving material from a chute not shown. It is provided with a bottompartition T? having a central aperture T This form of feeding means isparticularly adapted for coarse feeding or coarse crushing." Theaperture 1 is large and will admit relatively large particles. Thesefall upon the rounded or flattened top '1' of the head, the member Tbeing secured inposition as by the bolt T and having edge portions '1which engage the tops of the jaw plates K and K respectively. It thusserves not merely to clamp the jaw plates in position but to receive theparticles fed through the aperture T Referring to Figure 9, I illustratea screen,

, herein shown as a vibrating screen, having an upper screening memberV, and a lower screening member V The oversize from the screen Vmaterial which passes through the screen V but passes over the screen Vis delivered to the chute V which terminates as at V overlapping one ofthe members L The undersize from the lower screen V may pass ofi as bythe chute V not undergoing crushing. V" is any suitable surroundinghousing the side wall of which extends downwardly along the chute V asat V and downwardly below the chute W as at V The structure thus shown,in' association with the partition K definitely segregates the oversizeand the screened material, passing the oversize to one crushing cavityand the screened material to another. The upper edge of the member Kterminates closely adjacent the lower edge of the member V Therefore, itis substantially impossible for particles to escape from one line offeed to the other. slightly overhangs the partition K delivering all ofthe coarse feed to the far crushing hopper, in relation to the screen.The fine feed passes to the inner crushing member, as will be clear fromFigure 9.

, It will be realized that whereas I have described and shown apractical and operative device, nevertheless many changes might be madein the size, shape, number and disposition of parts without departingfrom the spirit of my invention I therefore wish my description anddrawings to be taken as in a broad sense illustrative and diagrammaticrather than as limiting me to my specific showing. In particular, I wishit to be understood that the size and shape of the crushing 'cavity andof the crushing part delimiting. the

crushing cavities can be widely varied. Also, the

particular lubricating means employed may be The lower edge of themember V I illustrate a multiple jaw crusher in which two separatecrushing cavities are defined by the two normally fixed jaw plates L andthe two jaw plates K, K on the movable head. Each crushing cavity may beindividually adjusted to open it up or close it down, to make it a fineor coarse crushing cavity. I illustrate, for example, the adjustableabutment members N against which each movable jaw is yieldingly drawn asby the hooks O and the springs 0 Each of the normally fixed jaws ispivotedas at L. No clamping will take place, inasmuch as I provide arolling contact formed by the lugs I)" at the rear of the jaw structure.As the jaw plates are readily removable a certain change or variation inthe thicknessor contour of the crushing cavities can be obtained bysubstituting jaw plates of different design.

As an overload release I provide a yoke struo ture generally indicatedas M which abuts against the flanges B of the frame and is drawnthereagainst as by the spring M In'response to a movement is notdirectly toward and-away from the opposed crushing plate L but may bedescribed as a species of arc, as shown in dotted lines in Figure 6.This tends to draw or hold the material undergoing crushing against theopfollow the .structure as shown in Figure 8 in which therounded memberT is in looking engagement with the tops of the jaw plates K and K beingdrawn downwardly thereagainst as by the spring T Also, I may provide afeed limiting or feed distributing plate as shown in Figure 7, which maybe used where an identical product is produced by both sides. the plate8*, by itself, or in connection with the overhanging apertured partitionS", will slow the feed down and limit it to the desired volume. It willbe understood that whereas the'forms of Figures 5 and '7 are adaptableto use with the machine when it is uniformly set with both crushingcavities identical, I may also if I wish, and with the same feedingmeans, vary the setting of the two crushing cavities. I may, forexample, wish a half inch product from one side and a three-quartersinch product from the other;

where I have a call for two not too dissimilar grades of material. I canproduce these different sizes from a uniform feed into both cavities.

It often happens, however, that it is necessary to crush entirelydifferent material. I illustrate an example of such a situation and asolution for it, in Figure 9. In that case I segregate the feed betweenthe two cavities. The chute V delivers large material to a coarsely setcrushing cavity. It will be noted that the shaft L of the right handcrushing cavity or crushing jaw is set more widely away from the headthan is the corresponding shaft L of the finer set or left hand cavity.The larger material, delivered along the chute V drops entirely into thecoarse crushing cavity. The partition K approaches so closely to thedischarge edge V of the chute W as to prevent any material from abovethe chute V penetrating to the fine crushing cavity. The chute V on thecontrary, delivers the finer material to the fine crushing cavity, thelower edge V of the chute substantially overhanging, the guard member LTherefore, when the head, as shown in Figure 9, is oscillated, it causescrushing to take place in two separate crushing cavities of differentcontours and of different discharge apertures. The fine feed goes to themore closely set .crushing'cavity and the coarse feed to the more openor coarsely set cavity.

I claim: g

1. In a jaw crusher, a frame, a pair of normally fixed jaws-mounted uponsaid frame, and a moving crushing member between said jaws and means foroscillating it, said moving crushing member being provided with acrushing face opposed to each of said jaws, and supporting means for"said moving crushing .'member. including a plurality of links pivoted tosaid member .and to said fra'me, the means for oscillating said movingcrushing member including an ec- In such case centric and means forrotating it, a sleeve surrounding said eccentric and a sliding bearingconnection between the exterior of said sleeve and said moving crushingmember, at substantially the same level as the connection between thelinks and the crushing member,

2. In a jaw crusher, a frame, a movable jaw mounted upon said frame andmeans for actuating it, said jaw being provided with a pair of crushingfaces, situated upon opposite sides of the jaw, supporting means forsaid jaw including upstanding links pivoted to the frame and to a lowerportion of the jaw, the pivotal connection betweenthe upper ends of thelinks and the jaw being below the crushing faces of. the jaw,

the means for actuating the jaw including an eccentric passing throughsaid jaw at a level generally the same as that of the pivotalconnections between the jaw.and the upper ends of the upstanding links,and sliding contact means intermediate said eccentric and jaw. I

3. In a double acting jaw crusher, a frame, a pair of normally fixedjaws mounted upon said frame, a moving crushing member located be tweensaid jaws and having a crushing face opposed toeach jaw, and supportingmeans for said moving crushing member, including a plurality of linkspivoted to said member and to said frame at opposite sides of saidmoving crushing member, the pivotal connections between the links andthe frame being separated by a greater.

distance than the pivotal connection between the links and the movingcrushing member, and means for imparting an oscillatory movement to saidmoving crushing member.

' 4. In a double acting jaw crusher, a frame, a

pair of normally fixed jaws mounted upon said frame, a moving crushingmember located between said jaws and having a crushing face opposed toeach jaw, and supporting means for said moving crushing member,including a plurality of linkspivoted to said member and to said frameat opposite sides of said moving crushing member, the pivotalconnections be-: .tween the links and the frame being separated by adifferent distance than the pivotal connection between the links and themoving crushing member, and means for imparting an oscillatory' movementto said moving crushing member.

5. In a double acting jaw crusher, a frame, a pair of normally fixedjaws mounted upon said frame, a moving crushing member located betweensaid jaws and having a crushing face op posed to each jaw, andsupporting means for said moving crushing member, including a pluralityof links pivoted to said member and to said frame at opposite sides ofsaid moving crushing member,

the pivotal-connections between the links and the frame being separatedby a greater distance than the pivotal connection between the links andthe moving crushing member, said links being upwardly and inwardly.inclined.

6. In a double acting jaw crusher, a frame, a pair of normally fixedjaws mounted upon said frame, a moving crushing member located betweensaid jaws and having a crushing face opposed to each jaw, and supportingmeans for said moving crushing member, including a plurality of linkspivoted to said member andto said frame at opposite sides of said movingcrushing memher, the pivotal connections between the links and the framebeing separated by a greater distance than the pivotal connectionbetween the links and the moving crushing member, and means forimparting an oscillatory movement to said mow-'- 1- it, a normally fixedjaw mounted on said frame and overhanging said movable jaw, said frameincluding upstanding portions and relatively extended plane; abutmentflanges along upper edges thereof, means-for releasably holding thenormally fixed jaw in position in relation to the frame, including abridge having opposed plane portions engaging and conforming to theabutment flanges of the side portions of the frame, means for holdingsaid bridge normally in position, including springs compressed beneathsaid flanges, alining and compressing members for said springs,including rods extending through said flanges and secured to saidbridge, abutment means at the lower ends of said rods, engaging saidsprings, adjusting means for adjusting the position of the normallyfixed jaw in relation to said bridge, including a generally cylindricalexternally screw-threaded plug positioned substantially midway betweenthe ends of said bridge and of a diameter of the order of the width ofthe crushing cavity, said bridge being screw-threadedly apertured toreceive said plug, means for rotating said plug in relation to saidbridge, said plug including an inward face,,rocking contact meansbetween said inward face and an opposed portion of the normally fixedjaw, a compression member passing through said plug and'secured to theinterior thereof, and including a portion engaging said normallyfixedjaw in a securing relationship, and means for drawing saidcompression member and jaw-in the direction of said rocking contactmeans.

8. The structure of claim '1 characterized by the employment ofyieldingfmeans tending normally to draw said normally fixed jaw againstsaid plug.

9. The structure of claim '7 characterized by the employment of arocking contact between the plug and the normally fixed jaw, including arocker abutment extending horizontally along the rear face of said jawand projecting outwardly from said rear face.

10. The structure of claim .7 characterized by the employment, inconnection with said plug, ofmeans for looking it against unintendedrotation. v I

11. The structure of claim '1 characterized by the employment, inconnection with said plug, of means for locking it against unintendedrotation comprising a cover plate for the bridge aperture which receivessaid plug, and compression connections between said cover plate and saidplug, whereby the threads of said plug are locked against the threads ofsaid aperture.

12.'The structure of claim 7 characterized 'bythe employment of externalmeans eflective for rotation of said plug,'and means for locking saidexternal means and plug against unintended rotation.

13. In a jaw crusher. a pair of normally fixed jaws,,a moving crushingmember located between said fixed jaws, means for oscillating it. aplurality of jaw plates mounted on opposite faces of said movingcrushing member, one being opposed to each of said normally fixed jaws,and thereby forming two crushing cavities, a unitary locking member andmeans for drawing it positively downwardly upon said moving crushingmember and against the upper edges of said jaw plates, a partitionmember mounted on and extending upwardly from and moving unitarily withsaid member, a feed spout including a normally fixedpartition alinedwith said first partition, and means for constantly maintaining aneffective operative relationship between said partitions, whereby allthe material delivered downwardly through the said spout at one side ofsaid fixed partition falls into one crushing cavity, and all thematerial fed downwardly through the feed spout at the opposite side ofsaid fixed partition falls into the opposite crushing cavity, the meansfor drawing the unitary locking member downwardly against the upperedges of said jaw plates extending downwardly through said firstpartition and said unitary locking member, to 'secure said firstpartition in relation to the moving crushing member.

14. In a jaw crusher, a frame, a movable jaw mounted on said frame andmeans for actuating it, a, normally fixed jaw mounted on said frame, andmeans for varying the distance between the opposed crushing faces of thecrushing cavity thus formed, including abutment means opposed to saidnormally fixed jaw, yielding means for urging such jaw against saidabutment means and means for adjusting said abutment member toward andaway from the crushing cavity, said normally fixed jaw being pivoted inrelation to said frame, and rolling contact means intermediate saidnormally fixed jaw and said abutment membenincluding a relatively planesurface on one of said members, a rockeron' the other generally arcuatein transverse cross section, said yielding means adapted normally tohold said normally fixed jaw against said abutment-memher with saidrocker abutting against said plane surface, and means for, limitingmovement of the abutment member towards and fromthe crushing cavitytomovem'ent axially of the abutment member.

15. In a jaw crusher, a frame, a movable jaw -mounted on said frame andmeans for actuating it, a normally fixed jaw mounted on said frame,means for varying the distance between the opposed crushing faces of thecrushing cavity thus formed including an abutment opposed to saidnormally fixed jaw, yielding r neans for urging suchjaw against saidabutment, and means for adjusting said abutment toward and away from thecrushing cavity including a hollow cylindrical'exteriorly 'screwthreadedmember associated with the abutment, a corresponding screwthreadedmember associated with the frame, means for limiting the movement of theabutment member towards and away from the crushing cavity to movementaxially of the screwthreaded member, and means for imparting relativerotation to the screwthreaded member, and a rocker member associatedwith the rear face of the normally fixed jaw, the abutment on saidcylindrical memher being opposed to said rocker and said yielding meansnormally urging said rocker member against said abutment member.

' OSCAR C. GB-UENDER.

